C程序打印三角形、正方形、圆形、矩形和多边形的面积，使用switch case语句

s=(float)(a+b+c)/2;
area=(float)(sqrt(s*(s-a)*(s-b)*(s-c)));

area=(float)side*side;

area=(float)3.14159*radius*radius;

area=(float)len*breadth;

area=(float)base*height;

#include<stdio.h>
#include<math.h>
main(){
   int choice;
   printf("Enter</p><p>1 to find area of Triangle</p><p>2 for finding area of Square</p><p>3 for finding area of Circle</p><p>4 for finding area of Rectangle</p><p>5 for Parallelogram</p><p>");
   scanf("%d",&choice);
   switch(choice) {
      case 1: {
         int a,b,c;
         float s,area;
         printf("Enter sides of triangle</p><p>");
         scanf("%d%d %d",&a,&b,&c);
         s=(float)(a+b+c)/2;
         area=(float)(sqrt(s*(s-a)*(s-b)*(s-c)));
         printf("Area of Triangle is %f</p><p>",area);
         break;
      }
      case 2: {
         float side,area;
         printf("Enter Sides of Square</p><p>");
         scanf("%f",&side);
         area=(float)side*side;
         printf("Area of Square is %f</p><p>",area);
         break;
      }
      case 3: {
         float radius,area;
         printf("Enter Radius of Circle</p><p>");
         scanf("%f",&radius);
         area=(float)3.14159*radius*radius;
         printf("Area of Circle %f</p><p>",area);
         break;
      }
      case 4: {
         float len,breadth,area;
         printf("Enter Length and Breadth of Rectangle</p><p>");
         scanf("%f %f",&len,&breadth);
         area=(float)len*breadth;
         printf("Area of Rectangle is %f</p><p>",area);
         break;
      }
      case 5: {
         float base,height,area;
         printf("Enter base and height of Parallelogram</p><p>");
         scanf("%f %f",&base,&height);
         area=(float)base*height;
         printf("Enter area of Parallelogram is %f</p><p>",area);
         break;
      }
      default: {
         printf("Invalid Choice</p><p>");
         break;
      }
   }
}

When the above program is executed, it produces the following output:
Run 1:
1 to find area of Triangle
2 for finding area of Square
3 for finding area of Circle
4 for finding area of Rectangle
5 for Parallelogram
5
Enter base and height of Parallelogram
2 4 6 8
Enter area of Parallelogram is 8.000000
Run 2:
1 to find area of Triangle
2 for finding area of Square
3 for finding area of Circle
4 for finding area of Rectangle
5 for Parallelogram
3
Enter Radius of Circle
4.5
Area of Circle is 63.617199